Model based Path Selection in a Bluetooth Low Energy, BLE, Mesh Network

ABSTRACT

A method for supporting the establishment of a path for transmitting a message in a mesh network, wherein said message is to be transmitted from a source node in said mesh network to a destination node, via one or more intermediary nodes, in said mesh network. The method comprises the steps of receiving, by an intermediary node in said mesh network, a path discovery message originating from said source node in said mesh network, said path discovery message comprising a path quality parameter, updating, by said intermediary node, said path quality parameter based on a quality of link associated with a node from which said intermediary node received said path discovery message, and broadcasting, by said intermediary node, said path discovery message wherein said broadcasted path discovery message comprises said updated path quality parameter. A complementary method and corresponding node are also presented herein.

TECHNICAL FIELD

The present disclosure generally relates to the field of Bluetooth LowEnergy, BLE, mesh networks and more specifically to a method forselecting one path between a source node and a destination node in a BLEmesh network.

BACKGROUND

Bluetooth Low Energy, BLE, is a low-power, low-rate wirelesscommunications technology operating in the unlicensed 2.4 Giga Hertz,GHz, Industrial Scientific and Medical, ISM, band. Typically, BLE nodesare inexpensive, but also constrained in terms of memory andcomputational resources.

Bluetooth Mesh networking is standardized by the Bluetooth SpecialInterest Group, SIG, and the first release of Bluetooth Mesh waspublished in July 2017. The solution is based on flooding usingbroadcasting over a set of shared channels—the advertising channels.Other networking forwarding mechanisms, such as routing, and other datatransfer methods or bearers, may be introduced in future versions of thespecification.

The Bluetooth Mesh specification builds on the physical layer and thelink layer of the Bluetooth Core specification, and these layers areimplemented in the BLE controller. Higher layers, like the BluetoothMesh network and transport layers, are defined in the Bluetooth Meshspecification and would typically be implemented in the host.

A node acting as a relay node in a Bluetooth mesh network scans for meshmessages. When a message is detected and received the node checks if itis the destination of the message. The message is later forwarded in themesh network by re-transmitting it so that the neighbours of the nodecan receive it. By means of this distributed mechanism the message isforwarded from node to node(s) in the network so that the messagearrives at the destination.

The 1.0 version of the Bluetooth mesh specification allows packets totraverse through the mesh network by means of what is referred to asflooding. This essentially means that all packets will be forwarded byall relays until the packet eventually reaches its destination. Thismethod has some obvious drawbacks, mainly in terms of causedinterference and energy performance, especially as the level of trafficin the network increases.

Subsequent versions of the mesh specifications are expected to implementmechanisms to limit packets to only be forwarded along specific pathstowards the intended receiver(s), thus reducing the traffic congestionin directions where forwarding does not help improving the probabilityof successful delivery. Paths need to be ranked and then selected basedon relevant metrics.

Bluetooth Mesh has a number of characteristics that make it differentfrom other mesh technologies that, in turn, make it difficult to selectan optimal path using existing methods. Some of these characteristicsare the following:

Links are unreliable, that is, successfully received messages are notacknowledged by the recipient. This means that any method that assumesan acknowledged link may not be applied to Bluetooth mesh

In a Bluetooth mesh network, it is expected that the node populationcontains nodes with large variations in node capabilities, ranging fromlaptops and smartphones to sensors powered by coin cell batteries. Thesenodes may have significant differences in receiver sensitivities whichis something that many existing methods do not account for.

Bluetooth Mesh utilizes a contention-based MAC scheme that does notinvolve any collision avoidance methods, such as “listen before talk” asused by Wi-Fi. This means that there is a significant risk for on-aircollisions which can greatly affect the quality of a link.

Bluetooth Mesh relies on packet repetitions to increase the reliabilityof the system. The number of repetitions to use for a transmission isselected by the transmitting node. This makes the number of packetrepetitions a crucial parameter to determine the quality of a link.Conventional methods of path discovery typically do not take this intoaccount.

Most existing methods typically aim to minimize the number of hops totraverse the mesh network from source to destination or to simply choosethe links based on channel quality measurements, such as RSSI. Neitherof these metrics provide the full picture of the link candidates inorder to be able to choose a link that is optimal, in the sense oflargest data delivery rate.

In order to include data delivery rate, a widely used metric in meshnetworking is the Expected Transmission Count, ETX. However, ETX relieson acknowledged links, whereas Bluetooth Mesh uses unacknowledgedtransmissions. Therefore a solution involving ETX cannot be used in BLEmesh.

Known methods do not consider the possibility of receivers withdifferent characteristics, the possibility that messages are repeatedover link to increase the reception probability, and the effect ofinterference on the measured quality of a link.

SUMMARY

An object of the invention according to the present disclosure is toprovide information about a multi-hop path between two nodes in a meshnetwork such that the multi-hop path relates well to the actualperformance of the path.

Another object of the invention according to the present disclosure isto provide a method a path selection in networks comprising nodes withdifferent receiver characteristics deployed in the same network. Themethod may also be implementable in networks with unacknowledged links.

In a first aspect of the invention, there is presented a method forsupporting the establishment of a path for transmitting a message in amesh network, wherein said message is to be transmitted from a sourcenode in said mesh network to a destination node, via one or moreintermediary nodes, in said mesh network. The method comprises the stepsof receiving, by an intermediary node in said mesh network, a pathdiscovery message originating from said source node in said meshnetwork, said path discovery message comprising a path quality parameterupdating, by said intermediary node, said path quality parameter basedon a quality of link associated with a node from which said intermediarynode received said path discovery message, and broadcasting, by saidintermediary node, said path discovery message wherein said broadcastedpath discovery message comprises said updated path quality parameter.

The present disclosure introduces a method to calculate a metric todescribe the quality of link that traverses an arbitrary number of hops.This metric may then, in turn, be used to choose the optimal pathbetween two nodes in a mesh network. Thus, this method may need to beperformed by every node in the mesh network. In order to establish apath between two nodes in the mesh network, the source node maybroadcast a path discovery message in the mesh network.

The aim of such a path discovery message is to establish one path as thepreferred path between a pair of nodes in the mesh network. The pathdiscovery message, comprises a path quality parameter that reflects thequality of path traversed by the path discovery message so far. Theintermediary node upon receiving the path discovery message updates thepath quality parameter based on the last link and forwards, the pathdiscovery message together with an updated path quality parameter.

It may be understood that any node in the mesh network, could inprinciple, be a destination node. The method presented in the firstaspect of the present disclosure, is to be performed by a node upondetermining that the node is not a destination node for the present pathdiscovery message. When however, it is determined that the node is thedestination node for the particular path discovery message, a differentset of steps may need to be executed. Such steps are further elaboratedin a second aspect of the present disclosure.

According to an embodiment, the step of updating comprises, determining,by said intermediary node, a Received Signal Strength Indicator, RSSI,value for said received path discovery message, updating, by saidintermediary node, said path quality parameter based on said determinedRSSI value.

It may be advantageous to consider that the path quality parameter isbased on the RSSI value. Therefore, upon receiving a path discoverymessage, the intermediary node also determines the RSSI value of theincoming message. The determined RSSI value may be used to update thepath quality parameter.

In an example, the step of updating further comprises retrieving, bysaid intermediary node, an RSSI to success probability function, whereinsaid function provides for a likelihood that a message is successfullyreceived by said intermediary node over said link for a given RSSI,converting, by said intermediary node, said RSSI value to a successprobability using said retrieved function, and updating, by saidintermediary node, said path quality parameter based on said successprobability. The node may implement said mapping in the form of a table,wherein possible RSSI values are associated with a correspondingprobability of receiving a message.

It may also be considered to implement a function in each node whereby aprobability of receiving an incoming message is mapped to the RSS value.Therefore, based on the determined RSSI value, a probability ofreceiving an incoming message may be determined. The path qualityparameter may then be updated using such a determined probability ofreceiving the incoming message.

According to an exemplary embodiment, the step of updating furthercomprises measuring, by said intermediary node, a channel occupancyassociated with said link, and updating, by said intermediary node, saidpath quality parameter based on said measured channel occupancy.

The intermediary node may, for example, also determine a channeloccupancy link of the link over which the incoming message was received.This may be helpful in determining a probability of losing the messagedue to collisions with other messages over the same link. Such a channeloccupancy parameter may be utilised with other parameters in order todetermine updated path quality parameter.

According to an embodiment, the step of updating further comprisesdetermining, by said intermediary node, a number of repetitions thatwill be used for said link updating, by said intermediary node, saidpath quality parameter based on said determined number of repetitions.

The step of determining said number of repetitions may comprise any ofretrieving, by said intermediary node, said number of repetitions thatwill be used for said link from said path discovery message, counting,by said intermediary node, a number of repetition messages that arereceived across said link. The skilled person may also consider updatingthe path quality parameter using other relevant parameters, such as, forexample, the characteristics of the receiver.

According to an embodiment, the path quality parameter is initially setto 1. The method presented in the first aspect of the disclosurecombines the RSSI measurements, with a model of the receivercharacteristics of each node as well as the probability off collisionand the number of retransmissions into a single metric. Such a singlemetric may, then be used to determine an optimal path between a pair ofnodes in the mesh network.

An advantage of the proposed method is that it provides informationabout a multi-hop path between two nodes that relates well to the actualperformance of the path, with regards to packet delivery rates.Furthermore, the method may be implemented without introducing anyoverhead in terms of new control messages or information that would beneed to be distributed through the network.

An advantage is that the method can be used in network withunacknowledged links, such as the BLE mesh network. Finally, thesolution accounts for the presence of heterogeneous nodes deployed inthe same network.

In a second aspect of the present disclosure, there is presented amethod for determining a path for transmitting a message in a meshnetwork, wherein said message is to be transmitted from a source node insaid mesh network to a destination node, via one or more intermediarynodes, in said mesh network.

The method comprises the steps of receiving, by said destination node,one or more path discovery messages, wherein each of said messagescomprising a corresponding path quality parameter, determining, by saiddestination node, from said received path discovery message, that saiddestination node is the intended destination node, updating, by saiddestination node, said path quality parameters, for each of saidreceived path discovery messages, based on a quality of link associatedwith a node from which said destination node received said correspondingpath discovery message, selecting, by said destination node, a path fromsaid source node to said destination node as being the path between saidsource node and said destination node based on said updated path qualityparameters, and unicasting, by said destination node, a discoveryresponse message to said selected source node using said selected path.

The messages or Protocol Data Units, PDUs, transmitted in the meshnetwork have header portion. The header portion, among others, comprisesan indication of the source node and the destination node. Each node canread the header portion in order to determine whether or not the node isthe intended destination node. It is noted that in a mesh network, eachnode could be a destination node. Therefore, a node upon determiningthat it is not the intended destination node for a particular pathdiscovery message may perform a method according to the first aspect ofthe disclosure and upon determining that it is the intended destinationnode may perform a method according to the second aspect of the presentdisclosure.

The destination node also updates the path quality parameter based onthe last hop of the path discovery message. The destination node shouldhave, in principle, received the path discovery message over severalpaths as a result of the flooding nature of the BLE mesh. The messagereceived over several path, each have an associated path qualityparameter. The destination node then selects a path as being the optimalpath based on the received path quality parameters. As a final step thedestination node sends a unicast discovery response message to thesource node. Such a discovery response message may comprise anindication of the selected path and therefore, the path to be used offuture communications by the source node to the destination node.

In a third aspect of the present disclosure, there is presented anintermediary node in a mesh network arranged for supportingestablishment of a path for transmitting a message in said mesh network,wherein said message is to be transmitted from a source node in saidmesh network to a destination node, via one or more intermediary nodes,in said mesh network. The intermediary node comprises receive equipmentarranged for receiving a path discovery message originating from saidsource node in said mesh network, said path discovery message comprisinga path quality parameter, process equipment arranged for updating saidpath quality parameter based on a quality of a link associated with anode from which said intermediary node received said path discoverymessage, transmit equipment arranged for broadcasting said pathdiscovery message wherein said broadcasted path discovery messagecomprises said updated path quality parameter.

It is noted that the advantages of the first aspect of the presentdisclosure being a method for supporting the establishment of a pathbetween a pair of nodes are also associated with the third aspect of thepresent disclosure being the intermediary node in the mesh network.

According to an example, the process equipment is further arranged fordetermining a Received Signal Strength Indicator, RSSI, value for saidreceived path discovery message, and updating said path qualityparameter based on said determined RSSI value.

In an embodiment, the process equipment is further arranged forretrieving an RSSI to success probability function, wherein saidfunction provides for a likelihood that a message is successfullyreceived by said intermediary node over said link for a given RSSI,converting said RSSI value to a success probability using said retrievedfunction, and updating said path quality parameter based on said successprobability.

According to an exemplary embodiment, the process equipment is furtherarranged for measuring a channel occupancy associated with said link,and updating said path quality parameter based on said measured channeloccupancy.

According to an example the process equipment is further arranged for,determining a number of repetitions that will be used for said link, andupdating said path quality parameter based on said determined number ofrepetitions.

According to a further example, the process equipment is furtherarranged for retrieving said number of repetitions that will be used forsaid link from said path discovery message and counting a number ofrepetition messages that are received across said link.

In a fourth aspect of the present disclosure, there is presented adestination node for determining a path for transmitting a message in amesh network, wherein said message is to be transmitted from a sourcenode to the destination node, via one or more intermediary nodes, insaid mesh network. The node comprises receive equipment arranged forreceiving one or more path discovery messages, wherein each of said pathdiscovery messages comprising a corresponding path quality parameter,process equipment arranged for determining, from said received pathdiscovery message, that said destination node is the intendeddestination node, and for updating said path quality parameters, foreach of said received path discovery messages, based on a quality oflink associated with a node from which said intermediary node receivedsaid corresponding path discovery message, select equipment arranged forselecting a path from said source node to said destination node as beingthe path between said source node and said destination node based onsaid updated path quality parameters, and transmit equipment arrangedfor unicasting a discovery response message to said selected source nodeusing said selected path.

It is noted that the advantages of the second aspect of the presentdisclosure being a method of determining a path for transmitting amessage in a mesh network, are also associated with the fourth aspect ofthe disclosure being a destination node for determining a path fortransmitting a message in a mesh network.

In a fifth aspect of the present disclosure, there is presented acomputer program product, comprising a computer readable storage mediumstoring instructions which when executed on at least one node of a meshnetwork cause said at least one node to carry out the method accordingto any one of the claims 1-8.

The invention according to the present disclosure is further explainedwith the help of drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a mesh network.

FIG. 2 schematically illustrates a method according to the presentdisclosure.

FIG. 3 schematically illustrates a method according to the presentdisclosure.

FIG. 4 schematically illustrates a mesh node according to the presentdisclosure.

FIG. 5 schematically illustrates a mesh destination node according tothe present disclosure.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a mesh network 10. The mesh network 10is, for example, a Bluetooth Low Energy, BLE, mesh network. The meshnetwork 10 comprises of several nodes 11-18. A single node may alsocomprise of further elements. Nodes communicate with one another bysending messages in said mesh network. The messages originate fromsource node and are intended to be received by a destination node(s).The destination may also be a group of nodes that are collectivelyidentified by a group address or a virtual address.

Especially in BLE mesh networks, it is conceivable that different typeof nodes are part of the network. For example, node 12 is laptop havinglarge processing power and a strong receiver. Nodes 14 and 16, forexample are sensors to activate lights in a room. Such sensors aretypically limited in processing capabilities and also have a weakreceiver. Node 17, for example is a mobile phone with Bluetoothcapability. Node 15, for example, is a low power node implementingenergy harvesting techniques such that it is not always on.

For example, 11 is a source node and 18 is the destination node. Underthe normal scheme of operation in BLE mesh networks, the messageoriginating in node 11 traverses nodes 12, 14, and 16 before reachingnode 18. Alternately, the message may also be routed through nodes 13,15, 17. Other combination of nodes in order to form a route from thesource node 11 to the destination node 18 may also be considered.

It is foreseen that in the future, in order to reduce the traffic in thenetwork and to thereby decrease the probability of loss of messages dueto collision, a preferred path between a pair of source and destinationnodes will be established and all messages originating at the sourcenode addressed to the destination node will take the same path. An aimof the present disclosure is to help in the establishment of such apreferred path.

FIG. 2 schematically illustrates a method 20 according to the presentdisclosure. FIG. 2 illustrates the steps to be performed by anintermediary node in the mesh network. In the above mentioned example,wherein the source node is node 11 and the destination node is node 18,the method is performed by all other nodes, i.e. nodes 12-17, in themesh network. In a step of receiving 21,the intermediary node, forexample 14, receives a path discovery message originating from thesource node 11 in said mesh network 10, said path discovery messagecomprising a path quality parameter. In a subsequent step of updating22, the node 14 updates said path quality parameter based on a qualityof link associated with a node 12, 13, 15 from which said intermediarynode 14 received said path discovery message. In a further step ofbroadcasting 23, the node 14 broadcasts said path discovery messagewherein said broadcasted path discovery message comprises said updatedpath quality parameter.

The step of updating 22, may comprise additional steps such asdetermining a Received Signal Strength Indicator, RSSI, value associatedwith an incoming message and using said RSSI value to update said pathquality parameter. It may also comprise determining a probability ofsuccessful reception based on said RSSI value. Other parameters such asreceiver characteristics, probability of collision, and the number ofretransmissions may also be considered during the step of updating thepath quality parameter.

FIG. 3 schematically illustrates a method 30 according to the presentdisclosure. FIG. 3 illustrates the method to be performed by adestination node in the mesh network. Continuing with the abovementioned example, node 18 is considered as the destination node. Themethod 30 comprises the steps of receiving 31, by the destination node18, one or more path discovery messages, wherein each of said messagescomprises a corresponding path quality parameter. A subsequent step ofdetermining 32, by the destination node 18, from said received pathdiscovery message, that said destination node 18 is the intendeddestination node. This may be determined by the node by examining aheader portion of the incoming message. If it is determined that saidnode is not the intended destination node, a method 20 illustrated inFIG. 2 may be performed by the node.

In a subsequent step of updating 33, the destination node 18 updatessaid path quality parameters, for each of said received path discoverymessages, based on a quality of link associated with a node 16, 17 fromwhich said destination node 18 received said corresponding pathdiscovery message. In a further step of selecting 34, the destinationnode 18 selects a path from said source node 11 to said destination node18 as being the preferred path between said source node 11 and saiddestination node 18 based on said updated path quality parameters.

For example, consider the situation wherein the destination node 18receives two path discovery messages originating from source node 11.One of these path discovery messages was routed through nodes 12, 14 and16 and has an associated path quality parameter p1. The other pathdiscovery message was routed through nodes 13, 15, 17 and has anassociated path quality parameter p2. The destination node compares thetwo parameters p1 and p2 and based on the result of the comparisonselects one path as the preferred path. Consider that the parameter p1was determined to be better after comparison.

The destination node 18 unicasts 35, a discovery response message tosaid source node 11 using said selected path. The discovery responsemessage is intended to provide information regarding the selected pathto the source node 11 and also the intermediary nodes 12, 14 and 16 inthis case. Therefore, the source node 11 knows the route over whichmessages are to be sent in the future. It may be foreseen that nodes aredynamically added to the mesh network thereby altering the topology ofthe mesh network. Therefore the methods 20, 30 may need to be performedperiodically in order to determine the optimal route in the meshnetwork.

FIG. 4 schematically illustrates a mesh node 40 according to the presentdisclosure. The intermediary node 40 comprises receive equipment 41, 42arranged for receiving a path discovery message originating from thesource node 11 in the mesh network, wherein the path discovery messagecomprises a path quality parameter. The process equipment 45 is arrangedfor updating said path quality parameter based on a quality of linkassociated with a node from which said intermediary node 40 receivedsaid path discovery message. It further comprises transmit equipment 43,44 arranged for broadcasting said path discovery message wherein saidbroadcasted path discovery message comprises said updated path qualityparameter. The node 40 also comprises a memory 46 arranged for storing acomputer program product comprising a set of instructions which whenexecuted by the processor 45 cause the node to perform a methodaccording to the present disclosure. The internal equipments maycommunicate with one another using the internal bus 47;

FIG. 5 schematically illustrates a mesh destination node 50 according tothe present disclosure. The destination node 50 comprises receiveequipment 51, 52 arranged for receiving one or more path discoverymessages, wherein each of said messages comprises a corresponding pathquality parameter. The destination node 50 further comprises processequipment 56 arranged for determining, from said received path discoverymessage, that said destination node is the intended destination node,and for updating said path quality parameters, for each of said receivedpath discovery messages, based on a quality of link associated with anode from which said intermediary node received said corresponding pathdiscovery message. The process equipment 56 may also be further arrangedto execute a set of instruction stored in the memory 57 which caused thenode 50 to perform a method according to the present disclosure.

The destination node 50 also comprises select equipment 55 arranged forselecting a path from a source node to a destination node as being thepath between said source node and said destination node based on saidupdated path quality parameters. The destination node 50 also comprisestransmit equipment 53, 54 arranged for unicasting a discovery responsemessage to said source node using said selected path. The person skilledin the art understands that since every node needs to be able toimplement both methods according to the present disclosure, the selectequipment 55 may also be incorporated in all the nodes in the network.

The method itself comprises three steps that may be performed in eachnode, the first step is to calculate the quality of the last hop linktowards the node in question, the second is to combine this this measureof link quality with the measure of the full path and the third is topropagate this measurement through the network. To calculate the qualityof the last hop link, we exploit the fact that each node may have someknowledge about its own receiver characteristics. These characteristicsallow us to model the receiver as a function that maps RSSI to aprobability of successful packet decoding.

Within each node, the function may be implemented as a simple look-uptable that maps the RSSI to success probability. This function may alsobe different for different nodes or different node types as it is basedon characteristics of the receiver of the node, which may differ basedon a number of factors, such as antennas or the quality of the receiver,as well as the transmission format (coding, modulation scheme, and framesize) being used.

Using the aforementioned function, the probability of successfullyreceiving a transmission over a single link, i, may be described as

P(Success_(i))=f _(i)(RSSI_(i))

When the path discovery message is forwarded to the next node, thecalculated success probability shall be included in the path discoverymessage, allowing it to be used by the next node. The next node may thencalculate its own last hop success, using the same formula as previouslymentioned. The probability of receiving a packet over multiple hops isthen easily calculated by means of multiplication with the value fromthe previous node, contained in the path discovery message. This isshown as

P _(agg)(Success_(i+1))=f _(i+1)(RSSI_(i+1))*P _(agg)(Success_(i))

where P_(agg) is the aggregated success probability, initialized to one(1) by the source node, i . . . , P_(agg)(success0)=1.

The method may then be extended to calculate the probability ofsuccessful reception over an arbitrary number of hops, as

${P_{agg}\left( {Success}_{I} \right)} = {\prod\limits_{i = 1}^{I}\; {f_{i}\left( {RSSI}_{i} \right)}}$

To find the optimal path between two nodes in a mesh network, one simplyneeds to select the path for which the calculated value of the successprobability is the highest.

Using only RSSI as a metric for link quality may yield misleadingresults as the RSSI value does not take interference into account. For asystem such as BLE that lacks channel coding, it is not an unreasonableassumption that a collision with another transmission will typicallyresult in a failed decoding. Given this assumption, the probability oflosing a packet due to a collision is the same as the channel occupancy.The channel occupancy can be easily measured by each node, and may thenbe used to adjust the calculated success probability for a given link.The following equation describes how the compensated probability iscalculated, where C denotes the channel occupancy.

P(Success_(i))=f _(i)(RSSI_(i))*(1−C_(i))

The probability of success for an arbitrary number of hops may then becalculated as

${P_{agg}\left( {Success}_{I} \right)} = {\prod\limits_{i = 1}^{I}\; {{f_{i}\left( {RSSI}_{i} \right)}*\left( {1 - C_{i}} \right)}}$

In a system, such as BLE mesh, where no per hop acknowledgements exist,transmissions may typically be repeated to increase reliability. Thisalso means that any method that tries to estimate the quality of a linkneeds to take into account the number of repeat transmissions that areperformed.

The number of repetitions that will be used for a link can be obtainedeither by including it in the path discovery message or by counting thenumber of messages that are received across that link. These could bepath request messages, assuming that the repetition parameters are thesame for the path discovery messages as for subsequent datatransmissions, or repetitions of regular data transmissions. It may alsouse a repetition value as signaled by the provisioner node in thenetwork. The following equation describes how the probability of successmay be calculated when the received messages in link i are expected tobe repeated Ni times.

P(Success_(i))=1−(1−f _(i)(RSSI_(i)))^(Ni)

The following equation shows the repetition compensated successprobability for a link with an arbitrary number of hops.

${P_{agg}\left( {Success}_{I} \right)} = {{\prod\limits_{i = 1}^{I}1} - \left( {1 - \; {f_{i}\left( {RSSI}_{i} \right)}} \right)^{Ni}}$

Using the methods described in previous embodiments, the skilled personmay also create a combined metric that compensates for both collisionsand repetitions of transmissions. The probability of success for a linkwith an arbitrary number of hops may then be described by

${P_{agg}\left( {Success}_{I} \right)} = {{\prod\limits_{i = 1}^{I}\; 1} - \left( {1 - \left( {{f_{i}\left( {RSSI}_{i} \right)}*\left( {1 - C_{i}} \right)} \right)} \right)^{Ni}}$

Other variations to the disclosed examples can be understood andeffected by those skilled in the art of practicing the claimeddisclosure, from a study of the drawings, the disclosure, and theappended claims. In the claims, the word “comprising” does not excludeother elements or steps, and the indefinite article “a” or “an” does notexclude a plurality. A single processor or other unit may fulfil thefunctions of several items recited in the claims. The mere fact thatcertain measures are recited in mutually different dependent claims doesnot indicate that a combination of these measures cannot be used toadvantage. A computer program may be stored/distributed on a suitablemedium, such as an optical storage medium or a solid-state mediumsupplied together with or as part of other hardware, but may also bedistributed in other forms, such as via the Internet or other wired orwireless telecommunication systems. Any reference signs in the claimsshould not be construed as limiting the scope thereof.

The present disclosure is not limited to the examples as disclosedabove, can be modified and enhanced by those skilled in the art beyondthe scope of the present disclosure as disclosed in the appended claimswithout having to apply inventive skills.

1-16. (canceled)
 17. A method for supporting the establishment of a pathfor transmitting a message in a mesh network, wherein said message is tobe transmitted from a source node in said mesh network to a destinationnode, via one or more intermediary nodes, in said mesh network, saidmethod comprising the steps of: receiving, by an intermediary node insaid mesh network, a path discovery message originating from said sourcenode in said mesh network, said path discovery message comprising a pathquality parameter; updating, by said intermediary node, said pathquality parameter based on a quality of link associated with a node fromwhich said intermediary node received said path discovery message; andbroadcasting, by said intermediary node, said path discovery messagewherein said broadcasted path discovery message comprises said updatedpath quality parameter.
 18. The method of claim 17, wherein said step ofupdating comprises: determining, by said intermediary node, a ReceivedSignal Strength Indicator (RSSI) value for said received path discoverymessage; and updating, by said intermediary node, said path qualityparameter based on said determined RSSI value.
 19. The method of claim18, wherein said step of updating further comprises: retrieving, by saidintermediary node, an RSSI to success probability function, wherein saidfunction provides for a likelihood that a message is successfullyreceived by said intermediary node over said link for a given RSSI;converting, by said intermediary node, said RSSI value to a successprobability using said retrieved function; and updating, by saidintermediary node, said path quality parameter based on said successprobability.
 20. The method of claim 17, wherein said step of updatingfurther comprises: measuring, by said intermediary node, a channeloccupancy associated with said link; and updating, by said intermediarynode, said path quality parameter based on said measured channeloccupancy.
 21. The method of claim 17, wherein said step of updatingfurther comprises: determining, by said intermediary node, a number ofrepetitions that will be used for said link; and updating, by saidintermediary node, said path quality parameter based on said determinednumber of repetitions.
 22. The method of claim 21, wherein said step ofdetermining said number of repetitions comprises either or both of:retrieving, by said intermediary node, said number of repetitions thatwill be used for said link from said path discovery message; andcounting, by said intermediary node, a number of repetition messagesthat are received across said link.
 23. The method of claim 17, whereinsaid path quality parameter is initially set to
 1. 24. A method fordetermining a path for transmitting a message in a mesh network, whereinsaid message is to be transmitted from a source node in said meshnetwork to a destination node, via one or more intermediary nodes, insaid mesh network, said method comprising the steps of: receiving, bysaid destination node, one or more path discovery messages, wherein eachof said messages comprises a corresponding path quality parameter;determining, by said destination node, from said received path discoverymessage, that said destination node is the intended destination node;updating, by said destination node, said path quality parameters foreach of said received one or more path discovery messages, based on aquality of link associated with a node from which said destination nodereceived said corresponding path discovery message; selecting, by saiddestination node, a path from said source node to said destination nodeas being the path between said source node and said destination nodebased on said updated path quality parameters; and unicasting, by saiddestination node, a discovery response message to said source node usingsaid selected path.
 25. An intermediary node in a mesh network arrangedfor supporting establishment of a path for transmitting a message insaid mesh network, wherein said message is to be transmitted from asource node in said mesh network to a destination node, via one or moreintermediary nodes, in said mesh network, said intermediary nodecomprising: receiver circuitry configured to receive a path discoverymessage originating from said source node in said mesh network, saidpath discovery message comprising a path quality parameter; processingcircuitry configured to update said path quality parameter based on aquality of link associated with a node from which said intermediary nodereceived said path discovery message; and transmitter circuitryconfigured to broadcast said path discovery message, such that saidbroadcasted path discovery message comprises said updated path qualityparameter.
 26. The intermediary node of claim 25, wherein the processingcircuitry is further configured to: determine a Received Signal StrengthIndicator (RSSI) value for said received path discovery message; andupdate said path quality parameter based on said determined RSSI value.27. The intermediary node of claim 26, wherein the processing circuitryis further configured to: retrieve an RSSI to success probabilityfunction, wherein said function provides for a likelihood that saidmessage is successfully received by said intermediary node over saidlink for a given RSSI; convert said RSSI value to a success probabilityusing said retrieved function; and update said path quality parameterbased on said success probability.
 28. The intermediary node of claim26, wherein the processing circuitry is further configured to: measure achannel occupancy associated with said link; and update said pathquality parameter based on said measured channel occupancy.
 29. Theintermediary node of claim 26, wherein the processing circuitry isfurther configured to: determine a number of repetitions that will beused for said link; and updating said path quality parameter based onsaid determined number of repetitions.
 30. The intermediary node ofclaim 29, wherein said processing circuitry is further configured toperform either or both of: retrieving said number of repetitions thatwill be used for said link from said path discovery message; counting anumber of repetition messages that are received across said link.
 31. Adestination node for determining a path for transmitting a message in amesh network, wherein said message is to be transmitted from a sourcenode to said destination node, via one or more intermediary nodes, insaid mesh network, said node comprising: receiver circuitry configuredto receive one or more path discovery messages, wherein each of saidpath discovery messages comprising a corresponding path qualityparameter; processing circuitry configured to determine, from saidreceived path discovery message, that said destination node is theintended destination node, and for updating said path qualityparameters, for each of said received path discovery messages, based ona quality of link associated with a node from which said intermediarynode received said corresponding path discovery message, and to select apath from said source node to said destination node as being the pathbetween said source node and said destination node based on said updatedpath quality parameters; and transmitter circuitry configured to unicasta discovery response message to said source node using said selectedpath.